A car with six times the power of your current car will not get you six times as fast to work or elsewere.

Obviously that's true, but the power isn't used that way in either the car or the camera. The article linked in the OP gives several examples of how the power is used.

I understand. My point was that only in certain circumstances it will matter. I believe it was the DigitalRev comparisson of the 600D and 650D (Digic4 vs Digic5) where was pointed out that there wasn't a significant difference due to the extra power, although Canon claims the 5 to be less noisy.

A Digic4 is still a nice performer (60D with in camera processing capability).